3.25.2008 - Prokaryotes

3.25.2008 - Prokaryotes - Prokaryotes Prokaryotes are the...

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Prokaryotes Prokaryotes are the oldest, structure. Simplest, and most abundant forms of life on earth o Abundant for over 2 billion years before the appearance of eukaryotes o 5000 different kinds currently recognized Prevalence of Prokaryotes Prokaryotic form o Bacillus (bacilli) straight and rod-shaped o Coccus (cocci) spherical shaped o Spirillum (spirilla) long and helical shaped Some bacterial colonies form spore producing structures Table 27.1 Feature Unicellularity. All prokaryotes are basically single-celled. Even though some bacteria may adhere together or form filaments, their cytoplasm is not directly interconnected, and their activities are not integrated and coordinated as is the case in multicellular eukaryotes. Cell Size. Most bacterial cells are only about 1 micrometer in diameter while most eukaryotic cells are over 10 times that size. Chromosomes. Prokaryotic DNA exists as a single circle in the cytoplasm, while in eukaryotes, proteins are complexed with the DNA into multiple chromosomes Prokaryotic Diversity Key classification characteristics o Photosynthetic or nonphotosynthetic o Motile or nonmotile o Unicellular or colony-forming or filamentous o Reproduction type – spore formation by division or transverse binary fission Kinds of Prokaryotes
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Very early, prokaryotes split into two lines o Archaea and bacteria are as different instructure and metabolism from each other as either is from eukarya. Domain Archaea – ancient bacteria (not ancient as (bacteria) – confined to extreme environments (early earth) Domain Bacteria – nonextreme habitats and include nearly all of the named species of prokaryotes Prokaryotic Diversity Comparing archaebacteria and bacteria o Plasma membranes Composed of different lipids o Cell wall Archaebacteria lack peptidoglycan in cell wall – mesh that strengthens o Gene translation machinery Archaebacteria similar to eukaryoets o Gene architecture Bacteria not interrupted by introns Prokaryotic Complexity Prokaryotic cell surface o Cell wall maintains shape and protects the cell from swelling and rupturuing Usually consist of peptidoglycan Gram-positive – thicker peptidoglycan Gram-negative – thinner peptidoglycan o flagella – slender protein – locomotion o pili – hairlike structures – attachment o endospores – resistant to environment The Cell Interior
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Internal membranes o Invaginated plasma membrane – function in respiration or photosynthesis
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This note was uploaded on 04/08/2008 for the course BIOL 1710 taught by Professor Jag during the Spring '08 term at North Texas.

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3.25.2008 - Prokaryotes - Prokaryotes Prokaryotes are the...

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